Cleaning of filter beds



May 2, 1939;

G. F. HURT CLEANING OF FILTER BEDS Filed April 7, 1957A I 4 sheets-sheet .1

Illimlll May 2, 1939. F, HU'RT 2,156,291

CLEANING oF FILTER BEDS l 4 Sheets-Sheet 2 Filed April 7, 1937 n TTB? May 2, 1939. G. F. HURT CLEANING OF FILTER BEDS Filed April 7.- 1957 4 Sheets-Sheet 25y INVENTOR ATTORNEYS May 4, 1939-' G. F. HURT I CLEANING OF FILTER BEDS I Filed April '7, 1957 4 Sheets-Sheet 4 ,m w, j .4 M ea bw, r /VV Z. e ya Mr im Cb, W

c/as ed a/:e/I dos ed 'i #ff/fer ed I5 I K ATTORNEYS I Patented May, 2, 1939v` UNITED STATES CLEANING F FILTER. BEDS George Fletcher Hurt, New York, N. Y., assgnor, by mesne assignments, to Jig-Action Filters, Inc., a corporation of New York Application April 7, 1937, SerialNo. 135,463

1s claims. `(ci. zin-12s) This invention relates to cleaning of filter beds, and includes both method and apparatus therefor; atypical instance being the cleaning of the granular or sand filter beds used in sewage filter- 5 ing. The invention is herein illustratively shown appliedto a sewage filteringl system of the kind in which the bed is immersed between the watery influent liquid to be filtered andthe ltrate liquid, with downow or upilow through the bed; espe, cially a filter of the downow type, the raw or dirty liquid passing down through the bed maintained on a submerged supportingv screen; the cleaning action and means preferably traveling over the bed progressively, or operating section by section, during' continuous filtering; but the prin.-

' ciples-of the invention may be useful on varioustypes of immersed bed filter, with or without travel, and combined or not with a preparatory settling reservoir. In referring to sand or granu- V vil() lar filtering mediumv is intended any hard small particles or grains; as of sand, rock, glass, metal or crushed mineral in loose form, and considerably heavier than water.

The known art comprises several kinds lof clean.

ing operations for downow or upiiow filters, with various principles of action, such as mechanical, hydraulic, magnetic, or combinationsk and'with various types of set-up or rig, of which some are described in an article on Mechanical ltration of sewage by P. B. Streander in the periodical Water Works 8i Sewage for July 1935. In a typical form ofl cleaning system vheretofore known, one section of the lter bed is cleaned at a timethe cleaning action, being repeated at shortintervals and the cleaning means or rigbeing travelled progressively over the bed, section by section, so that thel entire bed is acted'upon within a predetermined period. 'I'he cleaning action proper usually comprises the agitation of the sand of each successive section A40 accompanied by upow of the waterin 'thatsec- 50 terial or iloc, at each'section of the bed is with difficulty separated andjcarried away, lthus Arequir ing, at each upflow, that a large volume of water ubei-.caliid'up and overowed, suicient to dis- 'Y charge all the lloc lifted A'in that upflow. The removed water and oc invery low concentration thus enter a discharge compartment, whence they are removed to a suitable separation` or Adisposal place, while the cleaned section of lter bed resumes its office and the cleaning action vprogresses on to a succeeding section. Each of the `5 known systems operating on these principles has the above mentioned and other disadvantages, and none is entirely satisfactory.

Thegeneral object of the present invention is to aiord a satisfactory filter cleaning method and 10 apparatus that will be highlyv efficient and economical as well as simple and convenient of oper-v ation and control. AA further object is to secure thoroughness and uniformity of cleaning. ,A particular obj'ect is to dispense withV certain compli- 15 cations by making use of pneumatic action to cause a jigging water motion and uniform up .and down surges, at each section of the lter bed;

and thus to cause repeated and cumulative separations of alien solids or iioc from the sand, and 20 permitting progressive removal of the floc to a designated place, with improved elciency, and

higher concentration.

Other objects and advantages will appear in the herein following description of an illustrative em- 25 bodiment of the invention. To the attainment of such'objects and advantages the invention consists in the novel method of cleaning filter beds and the novel apparatus therefor, and the features of operation, combination, arrangement and 30 structure herein illustrated or described.

In the "accompanying drawings Fig. 1 is a top plan view of a lter cleaning apparatus embodying the present invention. v

Fig. 2 is a front or outer side elevation and ver- 35 tical section taken on the line 2-2 of Fig. l or Fig. 3 is a right end elevation and vertical secl tion taken on the line 3-3 of Fig. 2. f V

Fig. 4 is a partial top plan view showing certain 40 parts of Fig. 3 not appearing in Figs. l and 2, on a. smaller scale. l v

. Fig. 5, on a larger scale, is a front elevation of certain operating parts of Figs. 1 to 3, partly in vertical section on the line 5-5 of Fig. 3, showing 45 l the suction valve. I

Fig. 6 is a similar front elevationV on the line 6,-6 of Fig. 3, showing the relief valve. Fig. 7 is apartial left elevation partly in vertical section on the line 1-1 of'Flg. 5, showing 50 both valves. Y

Fig. 8 isa diagram illustrative of the preferredl character of actions. y l

On the accompanying. drawings the liquids are designated by distinctive references, as -follows.-

The influent or incoming liquid to be filtered is designated A, and afterit passes through the filter, preferably downwardly, it becomes the filtered liquid or filtrate B. A part of the liquid below the lter is by thisv invention drawn upwardly through the nlter and constitutes diverted liquid taking part in the cleaning of the illter, and is designated C. The varying levels of the liquids A and C are indicated by-small reference letters as hereinafter set forth. i

While the apparatus asa whole 'may take various forms,.such as elongated, with the actions y shifting longitudinally to and` fro, a circular form of filter chamber is preferably used, as will be apparent by considering Figs. 3 and 4, permittingl niche it affording a .supplemental space for regulation purposes.

The filter bed I5 is shown as submerged, being carried upon a screen or mesh I6 and thus suspended between the body A of influent liquid and the filtrate B. The filter bed may be composed -of sand, crushed minerals or other nely dividedmaterials suitable for the'purpose. The sand ii and foreign matter or floc i8 areshown diagrammatically in Fig. 8. i

A central reservoir iQ is indicated which may be utilized for preliminary clarifying or settling of the liquid to ybe filtered. This is shown as having an overflow' in the form of a pipe 2d delivering into theannular filter chamber 2i between walls i2 and I3. The overow pipe 2d isin the nature of a Weir and may be repeated at various points around the apparatus. rllhe filter chamber 2i has an extension within the niche id,- forming a control chamberA 22 useful for theop'eration of a device or iioat to regulate approximatelyv The mirate chamber es below the alter is' shown as delivering by an outlet pipe Zdwhich may pass to a convenientI point of disposal of the filtered liquid. In the outlet is shown a control valve 25 having an operating stem 2t. fisA arranged the stem. 2d is to be lifted to close further the valve, and vice versa. At its Vupper end the stem 2t is connected by an adjustable pivot 2. with an overhead or walking beam lever 23 fulcrumed on the wall id. rhe innerl end of the lever 28 extends over the control chamber 22 and fromit depends a float 29 partly immersed in the liquid A to be filtered.

By this control arrangement, whenthe liquid to be ltered isreceived at an excessive rate, tending to raise its level, the float 2d lifts and the valve 25 correspondingly opens, thus causing a more rapid delivery from the flltraae chamber, consequently an increased rate of filtering, and a lowering again of the level a' of the liquid to to be filtered. ,If the level a tends to drop exable cleaning" apparatus to travel progressively audaci around the annular chamber. 'Ihus a traveling carriage 32 is shown built up of longitudinal and transverse channels or otherstructural members. In Fig. 3 is shown a radial vbeam or bar 33which may be extended fromthe. carriage to a central pivot point, thus holding the carriage in proper relation to the chamber as it advances. The carriage is shown as provided with axles 34 carrying wheels 35'running on tracks 36 mounted at the tops of the walls l2 and I3 respectively. Having to travel further the frontor outer wheels may be larger than the inner' ones in the same :proportion as the respective radii from the center of the apparatus. In order to render self propelling, at a slow speed, the carriage and supportedapp'aratus, a motor 31 is shown mounted on the carriage and connected by reduction gearing 38 to the wheel axles 35.

The carriage 32 is used to support the cleaning part of the apparatus. There are shown four depending legs or hangers .39, two at each side of the carriage, and giving support to the submerged or partially submerged elements of the apparatus comprising what may be referred to as the caisson element lill, closed over. its top, andthe tank element di closed underneath and' preferably open at the top.v These combined elements are to be vertically adjustable so as to set them in proper relation to the top surface of the lte'r bed l5; and such addustment may be by means of the hangers 3'9 or by changing the relation of the carriage to its wheel axles. The carriage may be considered a traveling bridge from which hang the cleaning elementsthat progress along immersed in the influent liquid above the lter bed.

The caisson element dll is shown as having a transverse -wall t3 extending tothe full depth of the inuent liquid, and a second transverse wall` d@ spaced from the otherbut extending short of the full depth, and constituting a lute under which the liquid may ow. Connecting the caisarched, and the ends are closed by Alongitudinal walls d. By this housing construction the caisson element constitutes an inverted container or tank.' operating as a'bell or caisson. For the smooth travel of the wall d3 over the lter bed f the foot of this wall is shown as bent at dito afford a` substantial areaV of contactv upon the bed.

The tank'element di is formed with a bottom wall d@ at substantially the level of the foot il and traveling closely over the lter bed.- End walls ed may constitute continuations of the end walls d5 of the caisson, these two elements being thus combined as a rigid unitary apparatus. A transverse upright wall 5i is located inside the caisson, forming a weir, and at its extreme other end is a similar upright wall 52, completing theutank.

. Between these is an intermediate transverse wall caissond is the cleaning chamber 56, accommodating thecleaning liquid or water C. This chamber is formed between the upright walls'4 i3 and 5|. The liquid is shown at a low level c, and a highlevel c is indicated at which the surplus liquid overows the wall or weir 5I into the next or overflow" chamber 5l. The lower opening or mouth 55 loi the jig chamber 56 constitutes a wide entrance or slot for the cleaning water as it is sucked pneumatically up from the lter bed in each repeated cleaning operation.

The overow chamber 51 is enclosed between' the upright walls I and 44. It receives the liquid overflowing the weir 5I and there is indicated its'low level d and a high or maximum, level d'. From the chamber 51 the liquid vmay pass under the wall M, which acts as av lute, the liquid thus entering the discharge chamber 58 provided between the walls M and 53. Inthe discharge chamber the low and high liquid levels are indicated at e and e'. From the discharge chamber the liquid overows the wall or weir 53 into a `smaller* section than the overiiow4 chamber 51. It

is shown about half the section thereof, so that when the water rises from level d told' in chamber 51 it will tend to drop twice as far, from e to e in chamber 58.; thuscreatng a head between them tending to prevent water in chamber 51 rising enough to overflow back into chamber 56.

The normal level d is the same as e', determined by the discharge weir 53. The level e', or height of weir 53 may be either higher or lower than the outside liquid level a, within the purposes of this invention; but the level c', or height'of weir 5l, must be substantially higher than Weir 53 and at least as high and preferably higher than vthe level a.

The sump or wash-water chamber 59 is required to be progressively discharged to make room for further accretions. For this purpose there is shown provided a pump-62 'submerged below the low level of liquid in the sump. The pump 62 may be of the centrifugal type, suitablyl mountednear the bottom of thev tank, with an operating shaft 63 extending upwardly to a pumping motor 64 mounted on a bracket 65 .on the traveling carriage 32. The sump pump discharges upwardly through v a pipe 66 which may be carried to any desired point of disposal. The

liquid F in compartment 59 is thus kept between levels f and f.

With this invention it is essential to have the pneumatic jig or cleaner ,chamber 56 and means at every cycle or periodically. The jig chamber may have any shape,.though its walls are shown preferably upright.. The progressive removal means preferably comprises the overflow chamber 51, in a location to receive from the jig chamber, combined withmeans to remove excess liquidv from the-overflow chamber, without admitting air. This last removal means -is shown as comprising the discharge chamber or column 58, with an immersed passage between them constituting a seal or trap against admission of air tothe caisson. vPreferably also there is the fourth chamber or wash-water compartment 59 beyond. The chambers 58 and 58, however, could be combined as onefby having' the -pump 62. remove ex cess liquid directly from the former; but it is preferable to separate the functions of the third and fourth.A chambers, the weir 53 keeping the former substantially full notwithstanding that the pump sometimes maynearly empty, the lat'- ter. Between chambers 51 and 58 may be means to retard or .prevent undue liquid backilow. as a check valvel precluding return of overflow liquid back to the jig chamber. The walls 5| and 53 maybe considered parts of the caisson, with the wash-water compartment beyond them, and. its waalls preferably are'higher'than the wall or Weir 5 As will be more fully described the jigging or surging action ,within the cleaning chamber 56 `is herein provided by methodically varying the interior air pressure overvthe cleaning water, as

by `intermittent applications of pressure vchange or pneumatic suction. The upper part of the top wall 45 of the caisson is shown as having coupled with it an air pipe 68. Thisis of substantial diameter,"and for more prompt results there may .be several of these suction or air outlet ducts along the length'of the caisson, operated in unison. The suction pipe 68 is shown as extended vertically and then bent slantingly, and its end is coupled with a vacuum tank 69 mounted at a convenient' point on the carriage 32. The suction tank is preferably many times the volume of the caisson air space 54, above the liquid, and

there may be maintainedin the tank a moderate4 ,state of evacuation by means of an exhausting pipe 10 extending from the tank to a motordriven vacuum pump 1I. The suction pump 1I may be of any suitable type, as the Root blower, a rotary pump with self-contained drive motor. This is to be regulated in action, by change of speed or by a valve in duct 1li, so as lto maintain a predetermined degree of evacuation in vessel 69, preferably under the control of the pressure in the vessel, which is to be somewhat lower than,

or its suction slightly higher than, that desired to be applied to chamber 46. Such regulation of pressure may be on well known principles. The vacuum in the tank may also be varied automatically by reducing the suction slightly when the water level a rises, and vice versa, as by a float or control valve; this because less suction lift is needed when the influent level is higher.

The operation of this invention is to apply sucf tion to the chamber 56 by opening the duct 68 atintervals. thus causing at each operation an upward surge of liquid in the caisson, followed shortly by a relief to atmospheric pressure. liquid resurge downwardly, and repetition of cycle. To afford the intermittent suction action each suction pipe' 66 is shown as provided with a valve comprising an interior valve seat 13 underneath which engages a valve disk 14, the stem 15 of which extends upwardly through a stuiiing box 16, and at the top having a head 11 carrying'a cam follower or roll 18 operated automatically as will be described. Between the stem head and the stuiiing box is a compressed spring 19 tending to lift and close the, suction valve 14. 4

' In addition to the exhausting pipe or duct 68 leading from the caisson there is a relief pipe 82A v which, above, is shown open to the atmosphere so per; end of the stem 85 passes through the upper part of a guide bracket 88, which also carries the guide bar 86.' At the tcp of the stem is an enlargement or head 89 which passes above and is .vertically slotted to accommodate the cam shaft 93 to be mentioned. The head 89 carries above the shaft acam follower '98, the lifting of whichV opens the valve 8f3.-

The suction valve M and the relief valve 8d are to be operated in coordination to apply suc- A tion and pressure alternately to the caisson air space ft above the cleaning liquid C therein. Insteadpf relieving the exhaustion or partial suction of the "caisson by admitting 'atmospheric pressure by the valve-St, manifestly air under elevated pressure may be admitted by the opening of this valve; and the air pump ll, above described, while providing a suitable degree of suctionv for the valve l may' at the same timethere is shown an operating shaft Q3 turning in a front bearing bracket 9@ and a rear bracket 95.

This shaft carries a cam @l for operating the suction valve l, the cam having an elevation ,gli with a short dwell which, when in eiect,- holds Athe valve open against spring 79 and air pressure. The shaft carries also a cam $5 for operating the relief valve 8f3, this having an elevation IUD with a prolonged dwell holding open the relief valve against its spring at a time when the suction valve is closed. The coordinated cams ill and 99 operate respectively on the followers l@ and 90 to open the respective valves in predetermined alternation.

The cam shaft 93 may he rotated at a suitably slow speed, as two or three turns per minute, more or less, by means of a. drive motor H32 mounted on the carriage 32. This is avregulable electric motor vso that the shaft speed may be adjusted to the desired actions. The motor shaft m3 is shown operating through a conven- The contours and relative positions of the cams 91 and 9S onthe cam shaft determine the timing of the operation of the valves, and the cams may be changeable or adjustable. The shaft turning clockwise in Figs. 5 and 6, the relief valve 8S has closed, and both valves are closed, but shortly the suction ,valve will be opened by the cam 91, this being a quick opening, aiording a sudden application ofsuction and startingv the upward surging movement or pulsation in an abrupt manner highly effective for the opening up of the iilter bed structure and the dislodging or scrubbing of the oc from the heavier sa-nd particles.

The disclosed apparatus may be modined to extend the filter-chamber, namely, by reducing the diameter of chamber inner wall i2 until it is `but a central abutment or circular pier, -solid or will then be substantially of sector shape, each i 75 reaching from peripheral wall -to central pier,v

and the suction mouth 55, of similar shape, will progressively reach every section of the for cleaning thereof.

While the operation of this invention has been generally indicated it requires elaboration to explain fully the principles of the invention. The sewage may come to the filter as the raw dirty liquor, without clarification; or it may be ilrst clarified and then come to the' lter as influent containing say between 90 and 120 parts or pounds' per million of iloc or suspended solidl matter in the water, and this'inuent may then be filtered approximately to a` condition of only 20 to 30 parts per million, proper for. discharge. The heaviest and lightest impurities having been readily removed by previous settling and iiotation, the floc to be handled is nearly'lof the specific gravity of water and therefore troublesome. While the inuent is shown entering the annular filter chamber or vessel from the center andthe eliiuent leaving peripherally'theseows may be reversed or variously arranged. Y

The influent liquid A is maintained approximately at the depth or head a by the automatic valve 25, this steady depth being important since .the cleaning operations arevdependent upon the maintenance of .approximately correct relative levels in the filter chamber 2l for the best action. The-head a may be adjusted by ,means of the device 2l between the valve stem and float lever.

. The depth may be say 15 iinches about a 9 inch filter bed. The depth a above the filter also affords the head for filtering purposes. The

accumulating floc or ne solid particles or akes gradually occupy and block the interstices at the upper side of the lter bed, clogging the flow I through it and impairing its capacity. This gradual increase in the loss of head through the filter is oifset by the gradual opening up of the valve 25, so that the;x level a of inuent liquid may be maintained. i

The cleaning of the lter bed herein is by what may be described as a pneumatic jig action, involving alternate induced upow or surge and downsurge of the cleaning liquid or water C through `that portion of the filter bed which is beneath the mouth 55 of the cleaning chamber orcaisson. By varying methodically the inte- -rior air pressure .between a. relatively depressed and a relatively elevated pressure, preferably by the alternate application of air suction and relief, these'surging motions are brought about preferably with a substantially rhythmic rise and fall, each outrush of air starting the upow of cleaning water and the subsequent air inrush causing the return or ddwnilow.` The motions are of course the resultant of the interior pres,- sures, the exterior or atmospheric pressure and the hydraulic head, modified by the retardation of iow through the lter. 'I'he complete cycle may be varied in period according to requirements, and there may be for example several cycles per minute, or between about l0 and 40 seconds to each cycle. The optimum period for each-cycle, under given conditions, is readily determined by tests, and Will depend on the factors already mentioned including the Vnature Aof the oc, and the character'of the lter bed, i. e. the size and specic gravity of the lter grains or sand.

'Fordeseriptiom the suction tank, pipes and valve may be considered as a pneumatic means to apply depressed pressure to cause water upilow at intervals; while the relief valve ,is a relief means to cause pressure elevation of water downflow. The valve cams andtheir drive constitute -an automatic means or timed mechanism for be explained upon the diagram Fig. 8. The suction tank 69 may have a volume much larger than, for example eight times, the' normal vol,- ume of the-suction space 54 ,in the jig chamber Thepressure within the tank may be m'aintained subatmospheric to the extent of say about 9 inches of water column, so that when the valve 14 opens to connect the Atank and chamber the resulting suction will 'befslightly less or about that of a column of 8 inches of Water, more or less,.-

Which may fall off somewhat as the` water then rises. Much greater lair pressure variations may be used to give more emphatic actions. On Fig. 8 the cycles are represented betwee vertical lines, each line representing what may` be called the initial position, that of Figs. 5 and 6. The top two diagram lines show the valve actions, both valves being initially closed. The vacuum valve 14 first opens, preferably suddenly, andwithin 60 of cam advance it closes again as shown. After about 180 further rotation the relief valve 84 opens, and it remains so until it closes just before the completion of thel cycle. These specific descriptions it is to be understood are merely of an illustrative example.

The chamber air pressure within space 54 of the cleaner chamber 56 will be initially atmospheric, if compressed air'be not used. As valve 'I4 opens the pressure drops rapidly from atmospheric to the minimum, as the next sectionof the diagram shows, air rushingout through the valve to the tank until the suction is equalized, as at 8 inches of waterrcolumn. Here the depressed opens, the liquid' level rises.

abruptly and then more gradually until initial or atmospheric pressure is restored before the reliefvalve closes again Vnear the cycle end. v The diagram in the next section below Ishows approximately -the upflow and downflow of thecleaning water in the chamber and through the filter.

Starting gradually the rise accelerates, and then decelerates, and lbeyond the maximum, when pressure is restored, thewater resurges to its normal or low level. 'I'he action is smooth and may be roughly of sine character, substantially harmonic and continuous. The top of the diagram curve of watery level is shown dotted, representing a theoretical maximum rise, which however is not reached, the rise being-truncated by the weir 5I. Across the top of this Weir `a substantial portion of liquid overilows at the apex of each cycle, and falling into the overflow chamber 51 can not return, but eventually underflows the lute or seal wall 44 into the discharge chamber Stand thence to the wasli water compartment 59. v Thus, portl'on by portion, I

with a high percentage of entrained floc, the cleaning liquid escapes and is discharged for separate.

ing interrupted by the next upsurge, and minimum level c is therefore shown yslightly above inuent level a.

With the pressure drop, when valve 14 The action on the filter sand and associated lloc is that with each upsurge of water inthe cleaning chamber 46, the water, sucked from below through the filter bed, as the arrows show on Fig.2, tends to lift all the solids, loosening up the bed, separating the sand grains, especially inthe top stratum, giving access to. the alien matters A and lloc, causing detachment of floc from sand, grains and entraining all the solids upwardly into the chamber. A differential lifting action however prevails since the gravity ofthe illtergrains is substantially greater than that of the dis' lodged lloc. The floc rises more freely and higher,l While the sand grains in fact commence at once a relative descent or sinking through ,the`

rising current of water. This stage is followed by an intervening stage in which the Water is static and the sand grains substantially complete their return to the bed. When tire resurgel commences the filter grains are well below the higher portions of floc, and promptly resume their place upilow rate andA thuscan never reach the Weir nor be lost permanently, while the advancing rlse of the lighter floc is cumulative, exceeding each descent. These actions are completely distinguished from a known system in which the sand is caused to rise and the water relies on this for its rise and the floc relies on the water for its rise; the iloc being thus handicapped in favor of the sand, causing inefficiency in getting the fioc above the sand to overflow differentially, the wash-water being fico-poor. Y

In the-unal or lowest section of the diagram Fig. 8 is attempted to be roughly indicated the differential actqionby which'the floc is caused to rise relatively to the heavier sand in each cycle of upsurge and downsurge in the jig chamber. The

truncated water-surging action through several cycles has been explained, that part of the water. rising above the Weir level being caused to overiiow into the overflow chamber. Beneath this water surge diagram is shown a series of successive diagrammatic views or columns of the theoretical action, with six thereof to the cycle. The sand grains are indicatedby small circles and the iloc'particles by crosses, and the water by horlzontal lines.

`'At position l., snowing a theoretical column,

the water level is normal or low, and floc I8 andi sand I1 have not been acted' on. Column 2 lis taken at a midway point of upsurge, the watery floc and sand rising. A given small collection or group of sand grains islassumed, and a group of iloc particles, and-travel is ignored. Thefloc has ascended-`somewhat faster andhigher than the sand, though they are partly intermingled.

At column 3, the upsurge continuing, the differentiationis more apparent, and while both iloc and'sand have risen, the latter is seen to haveA relatively sunk -in the rising Water. Column 4 represents the apex of lupsurge; and rise -of oc and sand ceases. Between positions 3 and 5 the peak of the, upflow'passes over the Weir. The suction holds up thewater throughout this portion of the cycle. From positions 5 to 6 and to 1,

completing the cycle, there is downilow, the sand mined by the weir i. '51 the oc-laden liquid may not falljbelow level resuming its position in the bed and the oc group partially descending. Through all cycles the sand acts as described. being lifted but sinking and returning to the bed. 'I'he floc however having gained ascent starts the second cycle with -this advantage. as shown.

The second cycle greatly emphasizes the differential action, as the fioc group now` starts from a higher initial level. At positions 8 to .S to l5 the upsurge carries the iioc rapidly toward the Weir level, while the sand rises only vpart1y,.

as at positions 2, 3 and f3. At positions il, I2

and i3 the oc group moves somewhat down" ward with the downsurge, but this time its lowest level will be substantially higher than at po sition l; while the sand again returns substantially to the iilter bed.

In the third cycle the oc, starting well relevated, rises rapidly with the upsurge through positions iii, l5 and i6, so that at position i6 this, oc group, or a. substantial part of it, passes higher than the Weir level and is therefore carried over by the water from the jig chamber to the overow chamber. This is indicated by the.

distribution of the oc particles above and below the Weir level at position i6. At position l1 the overowed oc is omitted, and only apart of this group remains for the next downsurge.

Thus a principle of fioc separation and disposal is indicated which continues cycle after cycle. When the given loc group has thus commenced the overiiowing of the weir, the succeeding iloc groups, following immediately the one depicted, will be subject to the same action; Wherefore on every upsurge there will overflow a portion of water heavily laden with oc lifted relatively away from the filter bed sand. The

cleaning apparatus progressing over the uncleaned bed a fresh collection of ioc is presented, as for each cycle, and the cleaning water becomes more and more heavily laden with fioc; so that a vquite concentrated liquid passes'from chamber 56 through chambers 51 and 58 tothe wash water sump 59. The diagram lowest section for convenience has curves x, y and z applied indicating the theoretical or intended actions of the water, iloc and sand respectively, as described.

The operationmay be modified to enrich `further the wash-water, namely, by reducing the extent of each upsurge to prevent substantial overflow, for several cycles, while the oc becomes more and more concentrated in the surging water, and then by a higher upsurgefiowing d, while it may rise to d' by the suction above it, but must not pass back over theiweir 5|. The greater width of the chamber 51 sompared with the discharge chamber 58 tends to create rapidly a retarding head upon rise of level in 51, and supplemental retardation may be provided.v Chamber 51 therefore is always capacitated to vreceive a liquid portion over the Weir 5l. The column in chamber 58 cooperates. It may lower from the weir level e'to low level e due to suction rise in chamber 51."` By .theseactions a discontinuous but substantial liquid advance is maintained throughchambers 56, 51 and 58 to 59, with suicient agitation to keep the fioc entrained and prevent accumulation.

The described cleaning action on each successive sectionor zone of the filter bed is veryeffective. The' suction is self-distributing, assuring uniform action over the whole area exposed at the suction mouth. Each water upiiow acts upon the` full depth of the bed. A forcible and abrupt lift is given such as is best to cause the sand to separate from the floc. The cleaning means hereof is simple, rugged and durable. It involves no mechanical operation or agitation to be carried on in the filter bed or suction chambei' or below the water level; no water nozzles or jets are necessary, nor any special or expensive filter medium such as magnetic sand. Remote pneumatic control herein performs all the active functions. No special adjustments at the caisson have to be made, such as the levels of weirs. The action of the invention is adaptable to variations of conditions by simple adjustments effected at the traveling carriage; for example, slowing the cam speed and period of cycle thus giving ample time to ensure resettlement of sand, or speeding up for faster action with heavier sand; altering the degree of suction to regulate the surge and thereby the concentration of fioc in the wash-wateri vrelatively timing the cam actions, etc. The smoothness of the lter bed top surface is not disturbed since, with upright chamber walls, the depressed air pressure causes vertical upow and all sand particles merely rise vertically and tend to descend-to the same place in the bed.

l claim; Y

. l. In a filter cleaning. apparatus for a illter bed immersed between 4the inuent v.water Aoi? liquid to be nltered and the filtrate, in combination, a partly immersed cleaner chamber having its upper partpneumatically. closed above the general level of the liquid in which lthe iilter is immersed and having an immersed open mouth closely above therfilter bed, anl overow chamcleaner chamber to the overflowv chamber ior liquid overiiow substantially above the general liquid level, a'third chamber adapted to receive liquid from the overflow chamber and an underflow liquid passage from' the overflow chamber to the third chamber, with means for' removing liquid from said third chamber, a pneumatic means comprising a suction source and a suction passage between said suction-source and cleaner chamber and a. suction controller operable at intervals to apply suction to the cleaner chamber thereby to cause cleaning liquid upflow through the lter bed and upsurge within the cleaner chamber to overflow intermittently therefrom, a relief means comprising. a passage between said cleaner chamber-'and the atmosphere and a relief controller operable after each liquid upow to relieve the depressed pressure in the cleaner chamber thereby to cause liquid downsurge within the chamber and downilow thereof into the filter bed, and automatic means to operate said suction and relief controllers in coordinated alternation, thereby-to cause successive upflows and downfiows of cleaning liquid and methodical overflowsfrom the cleaner chamber to the overow chamber.

'ber and an overow vpassage leading from the i 2. In a ltercleaning apparatus for a fllter bed immersed between the influent water` or liquid to be filtered and the filtrate, a partly immersed cleaner chamberhaving its upper part pneumatically closed above the general level of the liquid in which the lter bed is immersed and having an immersed open mouth closely above the iilter bed, an overflow chamber and an overflow passage leading from the cleaner chamberto the overow chamber for liquid overflow substantially above the general liquid level, a discharge chamber adapted to receive liquid from the overflow chamber and an underflow liquid passage from the overow chamber to the discharge chamber whereby the overow chamber is sealed against air inflow, said discharge chamber being of smaller sectional dimension than the overflow chamber whereby suction over the overflow chamber may not cause liquid reow into the cleaner chamber, va pneumatic means for methodically varying the interior air pressure over the liquid in the cleaner chamber, thereby to cause successive upflows and downflows of cleaning liquid and methodical overflows from the cleaner chamber to the overflow chamber.

3. In a filter cleaning apparatus for lter bed immersed between the influent water or liquid to be filtered and the filtrate, in combination, a partly' immersed cleaner chamber having its upper part pneumatically closed above the general level of the liquid in which the lter bed is immersed and having an immersed open mouth closely above the filter bed, an overow chamber and an overflow passage leading from the cleaner chamber to the overflow chamber for liquid overow substantially above the general liquid level, means for removing excess liquid. from a submerged part of the overflow chamber without admitting air theretoa pneumatic means comprising a suction source and asuction, passage between said suction source and cleaner chamber and a suction controller operable at intervals to apply suction to the` cleaner chamber thereby to cause cleaning liquid upflow through 'the filter bed-and rise thereof within the cleaner chamber ber.

4. In a lter cleaning apparatus for a filter bed immersed between the inuent water or liquid to be filtered and the filtrate, in combination, a. partly immersed cleaner chamber having its,up per part pneumatically closed above the general level of the liquid in which the filter bed is irnmerse'd and having an immersed openimouth. closely above the lter bed, a pneumatic suction means comprising asuction source ,and a suction valve between said suction source and cleaner chamber and operable at intervals t/o apply suction to the cleaner chamber therebyto cause cleaning liquid upflow through the lter bed and upsurge thereof within the cleaner chamber, a

/relief means comprising a valve between said vcleanerv chamber and a. source lof suction relief and operable after each liquid upsurge to relieve the depressed air pressure in the cleaner chamber thereby to cause liquid downsurge within the chamber and downow thereof' into the irlter bed. automatic means' to operate said' suction and relief .valves in coordinated alternation, thereby, to cause successive upsurges and downsurges of cleaning liquid, and means for methodically owing away from the cleaner chamber the top portions of such liquid upsurges.

^ 5. An apparatus as in claim 4 and wherein the means for flowing away the liquid comprises an elevated weir, higher than sthe general liquid level, over which the tops of upsurgesk overflow from the chamber, with means preventing air iniiow over such weir.

6. An apparatus as in claim 4 and wherein the means for flowing away the liquid comprisesV an elevated weir over which the tops of upsurges overiiow from the chamber, with means preventing ,air-inow over such weir; and the automatic means is timed to cause upsurge `to above the weir level, with pause or dwell therebeore relief and downsurge.

'1. In a lter cleaning apparatus for a. lter bed immersed between the influent Water or liquid to beA filtered and the filtrate, in combination, a shiftable cleaner chamber having its upper part extending above the normal general level of the liquid in which the filter bed is immersed and having an immersed open mouth closely above the filter bed, a. pneum'atic means connected with thecleaner chamber and operabe at intervals to apply to the cleaner chamber a change of air pressure thereby to cause a surge of cleaning liquid within the cleaner chamber, a relief means connected with the cleaner chamber and operable to relieve the changed air pressure in the cleaner chamber thereby to cause reverse liquid surge Within the chamber, automatic means to operate said pneumatic means andrelief means in a cycle of coordinated alternation, thereby to cause successive upsurges and downsurges of cleaning liquid, withresulting upiiow and downfiow through the filter bed, and means for methodically owing away from the cleaner chamber the top portions of such liquid upsurges.

8. An apparatus as in claim '7 and wherein the means for flowing away liquid comprises anoutow passage at such altitude as to permit overflow of the tops onl of upsurg'es,` and an airsealed chamber into which the outow passa/gev means for removing excess delivers and having liquid.

9. An apparatus as in claim 'Z and 'wherein said pneumatic means comprises an air tank-of relatively large volume, with connection tosaid chamberfafnd a control valve for said connection.

Valve and the relief means a relief valve, and

sufficient to hold up the liquid for an appreciable period at the top of each upsurge, during which the lifted filter medium returns toward the bed.

13. In a d'ownflow filter the combination with an immersed sand lter bed, of a traveling cleaner chamber having its mouth close against ,the bed topsurface, pneumatic valve means for providing air alternately at higher and lower pressures in the chamber, to cause up and down water surge in the chamber, a take 01T passage leading from the chamber for outiow of the tops of upsurges, and means for removing the water so outflowed. i

14. Apparatus for xcleaning a iilter bed composed of grains of material substantially heavier than the liquid or water and immersed between the influent and ltrate liquids, comprising a cleaner chamber supported with its mouth closely adjacent the upper side of the filter bed, means for methodically varying the interior air pressure over the cleaning-liquid thereby to cause the liquid to surge up and down in the chamber and through the bed, and means for progressively removing cleaning liquid from the chamber comprising a liquid outflow passage for owing away therefrom ,the top portions of liquid upsurges.

15. The method of cleaning a iilter bed composed of grains of material substantially heavier' 16. 'The method of cleaning anlter bed com.

posed of grains of material substantially heavier than the liquid or water and immersed between the -iniiuent and ltrate liquids, comprising maintaining a cleaner chamber with its mouth closely adjacent the upper side of the filter bed, methodically depressing and elevating the interior air pressure over the cleaning liquid thereby to cause the liquid to surge up and.' down in the chamber and through the bed, and progressively removing cleaning liquid from the chamber by overflowing therefrom the top portions of liquid upsurgfs,v and receiving the same in an air-sealed pressure over the cleaning liquid thereby to cause the liquid to surge up and down in the chamber and through the bed, and progressively removing cleaning liquid from the chamber by owing away therefrom the top portions of liquid upsurges.

18. The method of claim 17 and wherein each cycle of operation is so conducted that the liquid upsurge is caused to open the granular bed, lift a group of i-llter grains and lift further a group of the lighter foreign matter, and so that the subsequent downsurge causes return of the grains to the' bed while leaving the group of foreign matter higher up; 'whereby the foreign matter progresses upwardly in successive cycles and i GEORGE FLETCHER HURT. 

